Device for electrostatic charging of a multilayer paper web

ABSTRACT

A multiple layer paper web is provided with an electrostatic charge for the purpose of adhering the multiple webs to each other. A pair of oppositely charged rollers contact the surface of the multiple layer printing aper web and impart the charge to the web. The pair of oppositely charged rollers are positioned directly before a cylinder folding group of a web-fed rotary printing press.

FIELD OF THE INVENTION

The present invention relates to a device for electrostatically charginga multilayer ribbon or paper web train.

DESCRIPTION OF THE PRIOR ART

It is generally known and described in EP 0 230 305 A2 that inrotogravure printing the incoming material webs or respectively paperweb train or ribbons, are made to adhere to each otherelectrostatically, which adheres is called ribbon adherence. Thestability of the material webs or paper web trains is increased by meansof this electrostatic interlocking, so that the danger of a formation ofcorners of the printed products in the folding apparatus is reduced.Electrodes, which are arranged at both sides of the material webs and ata distance from the material webs are provided for applying theelectrostatic charge.

In connection with this electrostatic charge, its low effectiveness onthe paper web train or ribbon is disadvantageous, so that it becamenecessary to arrange additional devices, for example electrostaticallycharged guide devices, as disclosed in EP 0 230 305 A2 in order toreduce the effects of the so-called whip action, which leads to theformation of corners.

DE 31 17 419 C2 describes a method for the electrostatic charging of amultilayer paper web train ribbon. Here, the ribbon is charged by meansof contactless acting electrodes after the webs have been broughttogether to form a ribbon downstream of a pair of compression rollers.

DE 27 54 179 C2 discloses a method for the electrostatic charging of amultilayer ribbon, wherein the edge areas of each layer are individuallycharged by means of rollers.

EP 0378350 A2 discloses a transport device for paper sheets in aplotter. This transport device has transport rollers forelectrostatically charging a paper sheet and a plastic sheet.

U.S. Pat. No. 4,462,528 A describes a device for holding a web. Thisdevice has brushes, by means of which the web is held electrostatically.

SUMMARY OF THE INVENTION

The present object of the invention is based on providing a device forthe electrostatic charging of a multilayer ribbon.

In accordance with the invention, this object is attained by the use oftwo rollers which press the ribbon or paper web train together and whichalso act as charging electrodes. Alternatively, the paper web train orribbon can be electrostatically charged by oppositely polarized chargeelectrodes in the form of electrically conductive brushes which touchthe paper web train or ribbon.

The advantages which can be achieved by means of the invention lie, inparticular, in that charging of the paper web train ribbon takes placein a manner which is so lasting, that further devices for preventing, orreducing the formation of corners can be omitted. For example, analready provided pair of drawing rollers, which is required for theoperation of the folding apparatus and has been modified in its designfor the purpose of transmitting a voltage, is used as the device forcharging the ribbon.

The strength of the voltage required for charging the ribbon is reducedin comparison with the voltage required by the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of present the invention are represented in thedrawings and will be described in greater detail in what follows.

Shown are in:

FIG. 1, a schematic representation of a longitudinal folding device, aswell as the ribbon entry into a cylinder folding group;

FIG. 2, a longitudinal section through one roller of a pair of rollersof the present invention in accordance with FIG. 1;

FIG. 3, a representation analogous to FIG. 2, but with a secondpreferred embodiment; and in

FIG. 4, a representation analogous to FIG. 2, but with a third preferredembodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A longitudinal folding device 3 with a pair of funnel folding rollers 4,as well as two pairs of rollers, for example, drawing roller pairs 6, 7,are arranged ahead of the entry for a multilayer ribbon 1, formed of forexample, a plurality of paper webs, into a cylinder folding group 2, forexample, of a folding apparatus of a rotary printing press. Thisstructure is depicted most clearly FIG. 1.

The cylinder folding group 2 has a cutter cylinder 8 and a collectioncylinder 9, which operates against the cutter cylinder 8 and, in turn,works together with a folding jaw cylinder 11. The printed products,which have been transversely folded in the cylinder folding group 2, aresupplied to a further processing station by means of a conveying device,for example a belt conveyor device which is not specifically shown inthe drawings.

The second pair of drawing rollers 7, arranged directly in front of theentry into the cylinder folding group 2, consists of a first roller 13,seated fixed in a lateral frame, and a second roller 16, which is seatedon a pivot arm or bearing element 14 as seen in FIG. 2. This secondroller 16 can be placed against the first roller 13 seated fixed in thelateral frame, with both rollers 13 and 16 of the second pair of drawingrollers 7 constituting the charging electrodes. The running paper webtrainer ribbon 1 is conducted between the two rollers 13, 16.

In accordance with a first preferred embodiment as seen in FIG. 2 bothrollers 13, 16 consist of a cylinder- or hollow cylinder-shaped rollerbody, a metal body 17, which has a shell 18 of a resilient covering ofreduced conductivity, for example rubber of a hardness of approximately85° Shore. The metal body 17 is connected, fixed against relativerotation, at both ends by means of hubs 19—only one end beingrepresented in FIG. 2—with the shaft journal 21.

The hubs 19 are fastened, electrically insulated, by means of ballbearings 22 in the bearing element 14. An insulation which consists, forexample, of respective bushings 23 of insulating material, for example aresin-bonded fabric, arranged between the pivot arm, or respectively thebearing element 14, and the ball bearing 22, which has a radial bore 24for receiving a cable feed 26. The cable feed 26 receives a feed line,for example a cable 27 which, for the purpose of transferring energy viaan intermediate ring 25, is pressed by means of a spring-loaded contactelement 28 against the ball bearing 22.

At its end remote from the roller 16 the shaft journal 21 is connected,fixed against relative rotation, with an annular flange 29, which, inturn, is in connection, fixed against relative rotation, via a piece 31of insulating material with a driveshaft 32.

Each one of the rollers 13, 16 of the second drawing roller pair 13 canbe separately driven. Moreover, the first roller 13 of the second pair 7of drawing rollers is connected with a negative pole of a d.c. source,not represented, of approximately 5 kilovolts, for example a hightension d.c. generator, and the second roller 16 of the second pair 7 ofdrawing rollers is connected with a positive pole of the d.c. source.The polarity can also be reversed.

The paper web train or ribbon 1 preferably consists of paper webs, whichare weakly mineralized and highly resistive.

It is also possible to drive only one roller 13 or 16 of the pair ofrollers 13, 16, or neither of the rollers of the pair of rollers 13, 16.

In accordance with a second preferred embodiment as seen in FIG. 3, bothcharge electrodes, which are designed as rollers 33, 34, also consist ofa cylinder- or hollow cylinder-shaped metal body 36, which has amulti-layer shell 37 comprised of with a lower, electrically insulatinglayer 38, a center layer 39 which conducts electricity well, and anouter layer 40, which is of only limited electrical conductivity.

At an end of each of the respective rollers 33, 34 a metallic contactring 42 is arranged on a roller end face. An interior diameter ofcontacting 42 is in connection with the shaft journal 43, and aperipheral surface of contact ring 42 is in an electrically conductingconnection with the electrically conducting center layer 39 of theroller shell 37. This can be achieved, for example, in that the contactring 42 has a shell-like contact surface 44 on its periphery, whichextends concentrically in respect to the metal body 36 and which in turnsupports contact tips 46, which are arranged on the end face ofcontacting 42 in a ring shape, are spaced apart from each other and areconnected with the material of the center layer 39 of shell 37 whichcenter layer 39 conducts electricity well.

The shaft journals 43—only one of which is represented—are seated in thebearing element 14 in bearings 47, which are also surrounded by aninsulating material 48.

A wiper element 49, which is fixed on the bearing element 14 and whichis insulated against it, is connected with the contact surface 44 of thecontacting 42, and is pressed by means of a spring force against thecontact surface 44. As in the first preferred embodiment, the wiperelement 49 is connected with a cable feed 26 4 and a cable 27.

In accordance with a third preferred embodiment, as seen in FIG. 4, therollers 51, 52 which act as charge electrodes, respectively each consistof a stationary shaft journal 53, fixed on the frame 14 in an insulatingmaterial 48 and having a roller body or metal body 36. The metal body 36is provided with an electrical high conductivity layer 39, for example asteel shell, above which an outer layer 40 of limited electricalconductivity is arranged. One bearing 47 is arranged on both sides orends of each of the rollers 51, 52 between the shaft journal 53 and thesteel shell 39.

The supply of electrical energy to the rollers 51, 52 takes By place viaa cable 27, which is in electrically conducting contact with the shaftjournal 53, for example with an exterior surface 54 of the shaft journal53.

It would, of course, also be possible to arrange the shell 39, 40fixedly on the metal body 36 and to seat the journals 53, electricallyinsulated and rotatably in the bearing element 14 fixed in place in thelateral frame. In this case the cable 27 would have to be connected bymeans of a collector ring with the exterior 54 of the shaft journal 53.

In accordance with a fourth preferred embodiment which is, notspecifically represented, the transfer of electrical energy to theribbon 1 can also take place by means of conducting brushes, for examplecarbon brushes, arranged on both sides of the material webs of theribbon 1.

It is furthermore possible to design the first and second rollers 13,16, 33, 34, 51, 52 of the second drawing roller pair 7 also in the formof so-called sandwich rollers.

Such sandwich rollers consist, for example, of a rotatably seated shaft,which receives a number of disks, which are arranged, fixed againstrelative rotation, on the shaft in the radial direction. Here, a diskmade of metal, for example steel, alternates with an adjoining disk,which consists of a metal body having an electrically well conductinglayer 39, and above it an outer layer 40 of limited electricalconductivity such as shown in FIGS. 3 and 4. Electrical energy isintroduced via the shaft journal.

Such a sandwich roller can be placed against a ribbon 1 as an individualroller, or also in opposing pairs, for example as a pair of drawingrollers.

When used in pairs, both sandwich rollers should be arranged in such away that a metal disk of the first roller is placed opposite a layereddisk of the second roller, and vice versa. Each roller of the pair ofrollers has a different polarity.

While preferred embodiments of a method and a for electrostaticallycharging a multilayer train or paper web ribbon in accordance with thepresent invention have been set forth fully and completely hereinabove,it will be apparent to one of skill in the art that a number of changesin, for example, the source of drive power for the rollers, the specifictype of printing press and folding group used and the like could be madewithout departing from the true spirit and scope of the presentinvention which is accordingly to be limited only by the followingclaims.

What is claimed is:
 1. A device for the electrostatic charging of amulti-layered paper web comprising: at least a first pair of cooperatingrollers, said pair of cooperating rollers defining a passage for saidmulti-layered paper web and pressing said multi-layered paper webtogether during passage of said multi-layered paper web between said atleast first pair of cooperating rollers; means for applying a firstelectrical charge to a first one of said pair of cooperating rollers anda second electrical charge, opposite from said first electrical chargeto a second one of said pair of cooperating rollers, said pair ofcooperating rollers applying an electrostatic charge to saidmulti-layered paper web during passage of said multi-layer paper webbetween said pair of cooperating rollers, said electrostatic chargeadhering layers of said multi-layer paper web together; and means toseparately drive each of said rollers in said pair of cooperatingrollers.
 2. A device for the electrostatic charging of a multi-layeredpaper web comprising: at least a first pair of cooperating rollers, saidpair of cooperating rollers defining a passage for said multi-layeredpaper web and pressing said multi-layered paper web together duringpassage of said multi-layered paper web between said at least first pairof cooperating rollers, said pair of cooperating rollers being drawingrollers; and means for applying a first electrical charge to a first oneof said pair of cooperating rollers and a second electrical charge,opposite from said first electrical charge to a second one of said pairof cooperating rollers, said pair of cooperating rollers applying anelectrostatic charge to said multi-layered paper web during passage ofsaid multi-layer paper web between said pair of cooperating rollers,said electrostatic charge adhering layers of said multi-layer paper webtogether.
 3. The device of claim 1 wherein each of said rollers in saidpair of cooperating rollers includes a metal roller body and an outershell of a limited electrical conductivity coating supported on saidmetal roller body.
 4. The device of claim 1 wherein each of said rollersin said pair of cooperating rollers includes a metal roller body and aroller shell supported on said metal roller body, said roller shellincluding an inner electrically insulating layer, an electrically highlyconductive center layer and an outer layer of limited electricalconductivity.
 5. The device of claim 1 wherein each of said rollers insaid pair of cooperating rollers includes a metal roller body includingjournals and further including bearing elements supporting saidjournals, an electrically highly conductive intermediate layer on saidmetal roller body, and an exterior limited electrically conductive layeron said electrically highly conductive intermediate layer.
 6. The deviceof claim 5 wherein said journals are electrically insulated from, andare fixed in place in said bearing elements and further wherein saidelectrically conductive layers of said rollers are rotatably supportedon said metal roller body.
 7. The device of claim 5 wherein saidjournals are electrically insulated from, and are fixed in place in saidbearing elements and further wherein said electrically conductive layersof said rollers are fixed in place on said metal roller body.
 8. Thedevice of claim 1 further including a support journal for each of saidrollers in said pair of cooperating rollers and an electrical feed linefor transmitting electrical energy to each of said journals of each ofsaid rollers.
 9. The device of claim 8 wherein each of said supportjournals has an outside surface and further wherein said electrical feedline to each of said support journals contact said outside surface ofeach said support journal.
 10. The device of claim 4 further including asupport journal for each of said rollers in said pair of cooperatingrollers, bearing elements receiving each of said support journals, anelectrical feed line for transmitting electrical energy and a wiper bodyin contact with said electrical feed line, said wiper body being fixedin place on said bearing element for each said roller and contactingsaid electrically highly conductive center layer, said support journalsbeing supported electrically insulated in each of said bearing elements.11. The device of claim 1 wherein each of said rollers in said pair ofcooperating rollers is a sandwich roller.
 12. The device of claim 1wherein said first roller of said pair of cooperating rollers isconnected with a negative pole of a high tension d.c. source and furtherwherein said second roller of said pair of cooperating rollers isconnected with a positive pole of said high tension d.c. source.
 13. Thedevice of claim 1 wherein said pair of cooperating rollers apply saidelectrostatic charge to said multi-layer paper web over an entire widthof said multi-layer paper web.
 14. The device of claim 1 wherein saidpair of cooperating rollers contact said multi-layer paper web after apoint of assembly of said multi-layer paper web, and contact outsidesurfaces of said multi-layer paper web.